Commit c0085404 authored by Adam Joseph's avatar Adam Joseph Committed by sternenseemann
Browse files

lib/systems/inspect.nix: remove isPowerPC 



Very confusingly, the `isPowerPC` predicate in
`lib/systems/inspect.nix` does *not* match `powerpc64le`!

This is because `isPowerPC` is defined as

  isPowerPC      = { cpu = cpuTypes.powerpc; };

Where `cpuTypes.powerpc` is:

  { bits = 32; significantByte = bigEndian; family = "power"; };

This means that the `isPowerPC` predicate actually only matches the
subset of machines marketed under this name which happen to be 32-bit
and running in big-endian mode which is equivalent to:

  with stdenv.hostPlatform; isPower && isBigEndian && is32bit

This seems like a sharp edge that people could easily cut themselves
on.  In fact, that has already happened: in
`linux/kernel/common-config.nix` there is a test which will always
fail:

  (stdenv.hostPlatform.isPowerPC && stdenv.hostPlatform.is64bit)

A more subtle case of the strict isPowerPC being used instead of the
moreg general isPower accidentally are the GHC expressions:

  Update pkgs/development/compilers/ghc/8.10.7.nix
  Update pkgs/development/compilers/ghc/8.8.4.nix
  Update pkgs/development/compilers/ghc/9.2.2.nix
  Update pkgs/development/compilers/ghc/9.0.2.nix
  Update pkgs/development/compilers/ghc/head.nix

Since the remaining legitimate use sites of isPowerPC are so few, remove
the isPowerPC predicate completely. The alternative expression above is
noted in the release notes as an alternative.

Co-authored-by: default avatarsternenseemann <sternenseemann@systemli.org>
parent f3fdc04f

lib/systems/inspect.nix

+0 −1
Original line number Diff line number Diff line
@@ -11,7 +11,6 @@ rec { 
    isi686         = { cpu = cpuTypes.i686; };

    isx86_32       = { cpu = { family = "x86"; bits = 32; }; };

    isx86_64       = { cpu = { family = "x86"; bits = 64; }; };

    isPowerPC      = { cpu = cpuTypes.powerpc; };

    isPower        = { cpu = { family = "power"; }; };

    isPower64      = { cpu = { family = "power"; bits = 64; }; };

    isx86          = { cpu = { family = "x86"; }; };

nixos/doc/manual/from_md/release-notes/rl-2211.section.xml

+16 −1
Original line number Diff line number Diff line
@@ -51,7 +51,7 @@ 
  </section>

  <section xml:id="sec-release-22.11-incompatibilities">

    <title>Backward Incompatibilities</title>

    <itemizedlist spacing="compact">

    <itemizedlist>

      <listitem>

        <para>

          The <literal>isCompatible</literal> predicate checking CPU
@@ -69,6 +69,21 @@ 
          compatible</emphasis>.

        </para>

      </listitem>

      <listitem>

        <para>

          The <literal>isPowerPC</literal> predicate, found on

          <literal>platform</literal> attrsets

          (<literal>hostPlatform</literal>,

          <literal>buildPlatform</literal>,

          <literal>targetPlatform</literal>, etc) has been removed in

          order to reduce confusion. The predicate was was defined such

          that it matches only the 32-bit big-endian members of the

          POWER/PowerPC family, despite having a name which would imply

          a broader set of systems. If you were using this predicate,

          you can replace <literal>foo.isPowerPC</literal> with

          <literal>(with foo; isPower &amp;&amp; is32bit &amp;&amp; isBigEndian)</literal>.

        </para>

      </listitem>

    </itemizedlist>

  </section>

  <section xml:id="sec-release-22.11-notable-changes">

nixos/doc/manual/release-notes/rl-2211.section.md

+3 −0
Original line number Diff line number Diff line
@@ -37,6 +37,9 @@ In addition to numerous new and upgraded packages, this release has the followin 
  `lib.systems.parse.isCompatible` still exists, but has changed semantically:

  Architectures with differing endianness modes are *no longer considered compatible*.



- The `isPowerPC` predicate, found on `platform` attrsets (`hostPlatform`, `buildPlatform`, `targetPlatform`, etc) has been removed in order to reduce confusion.  The predicate was was defined such that it matches only the 32-bit big-endian members of the POWER/PowerPC family, despite having a name which would imply a broader set of systems.  If you were using this predicate, you can replace `foo.isPowerPC` with `(with foo; isPower && is32bit && isBigEndian)`.





<!-- To avoid merge conflicts, consider adding your item at an arbitrary place in the list instead. -->



## Other Notable Changes {#sec-release-22.11-notable-changes}

nixos/modules/installer/cd-dvd/iso-image.nix

+1 −1
Original line number Diff line number Diff line
@@ -479,7 +479,7 @@ in 
                + lib.optionalString (isx86_32 || isx86_64) "-Xbcj x86"

                # Untested but should also reduce size for these platforms

                + lib.optionalString (isAarch32 || isAarch64) "-Xbcj arm"

                + lib.optionalString (isPowerPC) "-Xbcj powerpc"

                + lib.optionalString (isPower && is32bit && isBigEndian) "-Xbcj powerpc"

                + lib.optionalString (isSparc) "-Xbcj sparc";

      description = ''

        Compression settings to use for the squashfs nix store.

pkgs/development/compilers/ghc/8.10.7.nix

+1 −1
Original line number Diff line number Diff line
@@ -12,7 +12,7 @@ 
  libffi ? null



, useLLVM ? !(stdenv.targetPlatform.isx86

              || stdenv.targetPlatform.isPowerPC

              || stdenv.targetPlatform.isPower

              || stdenv.targetPlatform.isSparc)

, # LLVM is conceptually a run-time-only depedendency, but for

  # non-x86, we need LLVM to bootstrap later stages, so it becomes a